Student News

Graduate Research Achievement Day 2011

GRAD 2011 Highlights

Poster Symposium at the Odeum

Wednesday, March 31, 2011
1:00 - 4:30 PM

2nd Annual Innovation Presentation Competition

April 1, 2011
4:30-6:30 PM

Application of Computational Thermodynamics and Precipitation Kinetics to Light Weight Al Alloy Design

Danielle Belsito, Advisor: Prof. Richard D. Sisson Jr.


The U.S. Military needs structural materials for transportation vehicles that provide superior mobility as well as protection from the impact of improvised explosive devices (IEDs) and projectile artillery to increase soldier survivability.  To meet that need, new high strength, high toughness, light weight alloys are being developed.  This project focuses on an effort to develop an alloy made from a tri-modal powder consisting of a Al-5083 aluminum matrix with ceramic reinforcement particles.  Initial efforts at WPI’s Center for Heat Treating Excellence involve the development of multi-component phase diagrams, isotherms, and isopleths using thermodynamic and kinetic software, Thermo-Calc, Pandit and PrecipiCalc®, to predict the microstructure of this alloy and therefore performance.  Precipitation and dispersion hardening will be investigated, including the effect of potential cohesive precipitate-forming elements.  Additional factors affecting process results will also be examined, including the process control agents and cryomilling process parameters.  Finally, characterization of the powders and final coatings will be performed using TEM, SEM, XRD, and SIMS.

A Novel Method for Manufacturing Aluminum-Aluminum Nitride Nanocomposites

Cecilia Borgonovo, Advisor: Prof. Makhlouf M. Makhlouf


Aluminum matrix composites with micron-sized aluminum nitride (AlN) particle reinforcement are attractive engineering materials for many automotive and aerospace applications because of the many desirable characteristics of AlN; including its high thermal conductivity, strength, and hardness. The attractive characteristics of Al-AlN composites may be further enhanced by scaling the size of the AlN particles down to the nano range. Unfortunately, the potential for enhanced composite properties with such a decrease in the size of the reinforcing particles is often compromised by an increased tendency towards clustering and uneven dispersion of the particles in the matrix alloy. In this publication we present a novel manufacturing process in which the AlN particles are synthesized in-situ within an aluminum alloy by means of a controlled gas-liquid reaction in order to produce a composite material wherein submicron AlN particles are homogeneously dispersed in an aluminum matrix alloy. Also in this publication we present the mechanism of formation of the AlN particles and we discuss the effect of the chemical composition of the matrix alloy and the reacting gas on the efficiency of the aluminum nitridation reaction.

Costing of Heat Treatment Process

Yuzhong Cao, Advisor: Prof. Richard D. Sisson Jr.


Cost model is crucial to modern heat treatment industries’ survive and success.  With rising cost of energy, tighter specification on products quality and enhanced regulation on environment impacts, traditional heat treatment industries have to adapt cost model instead of traditional experience or trial and error to survive. Activity Based Costing Model (ABC) is a powerful costing model resulted by modern manufacturer’s concern on increasing overhead costs. Based on identify the activities that are the real cause of the overhead,  ABC assigns manufacturing overhead costs to products in a more logical manner than the traditional approach of simply allocating costs on the basis of labor hours. However, heat treating industries are facing far more difficulty to apply ABC method than other manufactures due to specificity in heat treatment process. In this research, two heat treatment processes, through hardening and carburizing, are the chosen for the cost model. First step is to exam the process and identify the activities, as well as different resources needed in manufacturing. The activity cost is calculated by sum up all the resources it consumed.  Then costs are assigned to products based on used activities. Process parameters, like dimension, grade, process time, temperature, are linked to costs by this cost model.

Novel Materials and Evaluation Methods for Elevated Temperature Applications

Xiang Chen, Advisor: Prof. Diana. A. Lados


This project is aimed to answer two important Materials Science questions.  First question is how do we develop high strength lightweight metal matrix nano-composites (MMnCs) with high creep and fatigue resistance at elevated temperature using effective and energy efficient casting methods?  Optical, scanning, and transmission electron microscopy results to date clearly indicate that the original approach taken in this study resulted in the development of a novel casting process and a new class of cast aluminum alloys strengthened by nano-size ceramic particles.  Second question is how do we evaluate the behavior of materials, including the newly created MMnCs, at elevated temperatures?  Specifically, for high temperature applications, the materials’ responses under both tensile and compressive creep-fatigue conditions are important, and need to be fundamentally understood.  In this study, the responses of conventional and MMnCs aluminum alloys under Hot Compressive Dwell (HCD) conditions will be investigated.  The HCD is a particular phenomenon when creep occurs under compressive stress, and is responsible for crack initiation and accelerated crack propagation in high-temperature components such as the automotive engine.  Despite its importance, the HCD has been largely ignored in previous studies.  A physics-based approach able to quantitatively predict HCD effects on the growth of fatigue cracks will be developed.  Experimental tests, able to assess this behavior, were specifically designed, and they will be discussed together with anticipated results and their relevance to structural design.

Development of Aluminum-Dross Based Materials for Engineering Applications: Reduce land filling and energy usage to recover Al

Chen Dai, Advisor: Prof. D. Apelian


Aluminum Dross is a by-product of Aluminum production.  At present, dross is processed in rotary kilns to recover the Al, and the resultant salt cake is sent to landfills; although it is sealed to prevent from leaching, the potential for leaching exists and harms the environment as the salt cake contains Fluorides and other salts. Furthermore, much energy is consumed to recover the Al from the dross; this is energy that can be saved if the dross could be diverted and utilized as an engineering material.  So the objective of the project is to eliminate ineffectively “refurbishing the waste“, and instead utilizing the waste in a natural cycle (closed loop) by using it as an engineered material.  Specifically, we are investigating three avenues:

  1. Use dross to make Al composites. We have found that dross powders are well dispersed in aluminum alloy matrix via friction stir processing; the product provides superior wear resistance with some sacrifice in strength. This certainly is a viable use of Al dross.
  2. Use dross as a high temperature additive for de-sulphurizing steel slag. The dross could be used as an additive to the slag to modify the chemistry.  However, for this application, only primary dross can be considered, because we need to alleviate fluorides in the dross.
  3. Use dross to make refractory materials such as brick, or used in concrete as filler. We have found that dross particles can be mixed well with cement. This improves stiffness, abrasion resistance, and controlling micro-cracking of the material.

How do we Design Structural Materials for High Performance under Dynamic Loading

Anastasios G. Gavras, Advisor: Prof. Diana A. Lados


Fatigue failures account for the vast majority of failures in most engineering components, either as a result of pure mechanical loading or in conjunction with other phenomena such as corrosion (corrosion fatigue), rolling contact between surfaces (rolling contact fatigue), sliding and friction between surfaces (fretting fatigue), and operation at elevated temperatures (thermo-mechanical fatigue and creep fatigue).  Traditionally, design against fatigue was based on the “Safe Life” approach (Stress-Strain Amplitude versus Number of Cycles to Failure).  However, this approach is significantly affected by variations in surface conditions or defect distributions, which influence both crack initiation and total fatigue life.  In addition, the contributions of fatigue crack initiation and crack propagation cannot be individually understood and/or partitioned.  Most importantly, in the presence of pre-existing flaws the “Safe Life” approach often overestimates the fatigue life of the component.  In this work, the “Defect Tolerant” approach was investigated, with focus on both early and advanced stages of crack propagation.  The effects of the initial flaw size and materials microstructure were studied, and fatigue crack growth mechanisms at the microstructure level were identified for various loading conditions.  Furthermore, a data reduction strategy was developed to represent the materials resistance to fatigue crack propagation using a single, design curve.  Data predictions for other load scenarios were successfully done based on the developed design curves.  Recommendations for integrating materials characteristics into structural design for fatigue performance will also be presented and discussed.

In-Situ Synthesis and Characterization of PEI/MWCNTs supported PtRu electrocatalyst for Direct Methanol Fuel Cell

Xi Geng, Advisor: Prof. Jianyu Liang


In the present work, PtRu nanoparticles (NPs) were successfully assembled on polyethyleneimine (PEI) functionalized multi-walled carbon nanotubes (MWCNTs) via an effective and facile polyol reduction approach. During the synthesis, the amine and imine groups in polycationic PEI provided anchoring sites for the noble metal ions, and thus facilitated the in-situ deposition of PtRu nanocrystals on MWCNTs. Noncovalent Surface modification of MWCNTs with PEI was confirmed by FTIR and Zeta-potential measurement. The morphology, crystalline structure and composition of the hybrid material was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX), respectively. According to the SEM and TEM observation, small particle size and good dispersion of Pt-Ru NPs decorated on PEI-MWCNTs was achieved. The cyclic voltammetry tests indicated that PtRu/PEI-MWCNTs possessed large electrochemical surface area and exhibited enhanced electrocatalytic activity towards methanol oxidation in comparison with using acid oxidized-MWCNTs (O-MWCNTs) as catalyst support. The superior electrocatalysis properties of the PtRu/PEI-MWCNTs nanocomposite may be attributed to the ultrafine grain size and high dispersion of PtRu NPs in the presence of PEI. These results may shed light on the development of polyelectrolyte modified Pt/C-based catalyst for direct methanol fuel cell (DMFC)

Three Dimensional Simulation of Ring Gear Heat Treating – Distortion and Residual Stress

Morgan Guardino, Advisor: Prof. Richard D. Sisson Jr.


The carburization heat treatment process for a transmission ring gear has been modeled using Abaqus/DANTE to simulate heat transfer, thermal contraction, and phase transformation that occur during heat treating. The goal of this simulation is to identify the causes for distortion and to develop a process to minimize it. Some sources included in the finite element analysis (FEA) model are an initial residual stress state, the geometry of press quenching dies, and the variation of the heat transfer coefficient (HTC) due to uneven oil flow during quenching. Separate FEA models were created to investigate the effect of uneven fixturing during carburization and the variation of HTC on the gear surface during the slow cool after carburization. HTC calculations were done using FLUENT in ANSYS Workbench and the data was used in the DANTE model separately. The complete heat treatment model predicts the resulting out-of-roundness and out-of-flatness of the gear and can be used to determine the influence each step of the process has on the final distortion.

Nanostructured Anode Materials for High-Rate Lithium Ion Batteries

Ryan Lawrence, Joe Gnanaraj, Advisor: Prof. Jianyu Liang


Nanostructured transition metal oxide materials are often cited for their excellent cyclability and high-rate capabilities as electrodes in lithium ion batteries. In this report, we synthesize CuO thin films on a copper substrate by means of a simple solution immersion and heat treatment. The morphology of such films is plate-like, making for greatly increased electrode surface area. CuO films are characterized by scanning electron microscope (SEM) and x-ray diffraction (XRD). The effect of solution time on the morphology and electrochemical performance is discussed. In electrochemical tests, half-cells made from CuO thin film anodes display excellent high-rate performance and reversible capacity.  The low cost, ease of synthesis, and electrochemical performance make CuO thin films an attractive anode material for lithium ion battery systems.

Characterization of Al-6Ni-xCu Alloys

Haohan Li, Advisor: Prof. Makhlouf M. Makhlouf


A brand new alloy was developed. The paper articulated the main microstructure of the Al-Ni system alloy, by adding Cu, the alloy is strengthened with precipitate hardening. With SEM, the one-dimensional lamellae structure of the Al3Ni is visualized and the dendrites during solidification can be clearly identified. A series of tensile tests were engaged and draw the conclusion of the mechanical properties. The cooling rate of the new alloy was also studied.

Hot Tearing in Cast Aluminum Alloys: Measures and Effects of Process Variables

Shimin Li, Advisor: Prof. D. Apelian


Hot tearing is perhaps the pivotal issue defining castability.  It is affected by alloy composition as well as processing conditions and variables.  Hot tearing is a complex phenomenon in that it lies at the intersection of heat flow, fluid flow and mass flow.  Over the years many theories and models have been proposed and accordingly many tests have been developed.  Unfortunately many of the tests that have been proposed are qualitative in nature.  The need exists for a simple, reliable, robust and repeatable quantitative test to evaluate hot tearing in Al cast alloys. WPI and CANMET MTL- both members of the Light Metal Alliance joined forces to address this need.  A quantitative hot tearing test was developed and the methodology is presented. Experiments were conducted utilizing the apparatus in studying the effects of process variables on hot tearing susceptibility for various cast alloys.  A protocol and standardized procedures that can be adapted by the metal casting industry has been established.

Molybdenum Electrode Performance in Glass Melting

Wendi Liu, Advisor: Prof. D. Apelian


The U.S. glass industry is a $28 billion enterprise and millions of tons of glass are melted each day by different heating techniques, such as conventional oil fired furnaces or via electrical heating. The share of electrical heating is bound to rise steadily because it is cleaner and more energy efficient. Due to this situation electricity will play a significant role in glass melting, either as all electric or by providing supplemental boosting. Molybdenum is the most frequently used electrode material to deliver the electricity into the glass melt. Although it has a high melting point, high electrical and thermal conductivity and a low coefficient of expansion, molybdenum electrodes will fail and have to be replaced from time to time. One of the current problems of molybdenum electrodes is the significant corrosion attack from the molten glass. Melt reaction with electrodes is the fundamental barrier to higher melting temperatures. Due to the corrosion of electrodes with redox reactions, the life of Mo electrodes is limited. Various studies have shown that the corrosion of molybdenum electrodes is a complex phenomenon; it depends on chemical composition of the electrode, current density and frequency, and chemical composition of the glass melt, specifically polyvalent ions that may be present in the melt. The objective of this project is to establish operative failure modes and mechanisms in Mo electrodes and to develop solution pathways to optimize electrode life by microalloying or via effective coating technologies.

Effects of Infiltration Time and Pore Size on the Morphology of Polymer Nanostructures Fabricated with the Solution Template Wetting Technique

Meghan Pasquali, Advisor: Prof. Jianyu Liang, Prof. Satya Shivkumar


The solution template wetting method is a simple, cost effective procedure that can be used to fabricate polymer nanostructures.  In this study, the solution wetting technique was used to form elongated polystyrene nanostructures within anodized aluminum oxide templates.  The effects of infiltration time and template pore size were studied to determine the role each plays on the final morphology of the nanostructures.  It was found that for PS solutions with high molecular weight polymer, hollow nanotubes can be formed for infiltration times <18 hr, whereas low molecular weight polymer solutions consistently form solid nanorods independent of infiltration time.  Additionally, relatively large pore diameters of ~200-300 nm are necessary to form hollow nanotubes.

Silver (Ag) – Carbon Nano Tube (CNT) Composite Fabrication

Rose Roy, Advisor: Prof. Jianyu Liang


Particles used on the nano-scale are much more reactive than their conventional macro-scale counterparts due to their greater surface area per weight.  Silver in particular has been proven to successfully kill viruses, parasites, bacteria, protozoan and other microorganisms. 

The creation of a silver-CNT composite with specific morphology is expected to provide an effective means at treating industrial wastewater in a simple and cost effective manner.  Carbon, traditionally used for water treatment, will be used to serve as a medium to support silver particles. The goal in this study is threefold; adhere silver nano-particles onto the CNT with control over dispersion and size, test its effectiveness to treat organic and biological matter in wastewater, and compare this nanocomposite with conventional carbon filter and chemical methods. The chemical reduction method is the most popular way to produce silver nano-particles without aggregation at high yield and low-cost.  By controlling various synthesis parameters such as concentration, pH, and additives, we can create silver nano-particles at the desired diameter. Scanning and transmission electron microscopy (SEM & TEM) are used to characterize the particle size and distribution. Preliminary results show an average particle size of 15nm on the CNT’s. By further adjustment of the synthesis conditions nanocomposites with desirable morphology will be ready for testing in the treatment of industrial wastewater.

Friction Stir Processing of Aluminum Cast Alloys for High Performance Applications

Ning Sun, Advisor: Prof. D. Apelian


As a recent outgrowth of the Friction Stir Welding (FSW) process, Friction Stir Processing (FSP) has been shown to eliminate casting defects and refine the microstructure at a pre-determined location; this results in improved mechanical properties and enhanced corrosion resistance. There is a growing need for Al metal matrix composites, and FSP is a viable means of producing components with localized composite structures. Such improvements have important implications for manufactured components for a variety of automotive and other industrial applications. In this project, we have verified and validated the potential of FSP processing to locally strengthen cast components, and to enhance mechanical properties. FSP is applied to alloys for localized microstructure manipulation, and the post-FSP heat treatments were carried out to explore the thermal behavior of the alloys post FSP.  In tandem we have also investigated the manufacture of localized composite zones that were made by the emplacement of a second phase into the Al alloy matrix and FSPed.

Electric arc discharge activated, diluted ammonia nitrocarburizing of 300-series stainless steels

Xiaolan Wang, Advisor: Prof. Richard D. Sisson Jr.


Case hardening of stainless steels (SS) has been a subject of continuing interest in the field of surface engineering. But the conventional, atmospheric-pressure, low-cost treatments of SS are ineffective due to the presence of chromia-rich films. This study presents results of nitrocarburizing different grades of austenitic SS (301, 304, and 310) using a modified, 4-hr long, atmospheric-pressure treatment method involving an electric arc-activated N2—25vol%NH3 blend with a carbon-sourcing gas addition not exceeding 2vol%.  Experimental procedures included laser analysis of furnace atmospheres, SEM-EDS, XRD, OM and Leco based, microstructural and compositional characterization of product layers, and evaluation of nitriding potential (KN) and activity (aN).  Rapid growth of hard (HK=~1100), nanostructured, nitride rather than carbide layers was observed on 301 shims at 565oC with growth rates exceeding 20 mm/hr.  In contrast, uniform, 15-20 mm-thick, expanded austenite S-layers were formed on 304ss at 500oC and 310ss at 565oC during the nitrocarburizing. 

Predicting the Response of Aluminum Casting Alloy to Heat Treatment

Chang-Kai (Lance) Wu, Advisor: Prof. Makhlouf M. Makhlouf


The objective of this project is to develop and verify a mathematical model that enables the prediction of the effects of heat treatment on cast aluminum alloy components. The model, which uses the commercially available software (ABAQUS), will accurately predict dimensional changes, distortion, and residual stresses in heat treated components. An extensive database is developed for an example aluminum alloy (A356) and includes the mechanical, physical, and thermal properties of the alloy all as functions of temperature. In order to verify the accuracy of the software predictions, the predictions are compared to their measured counterparts, where dimensional changes and distortion are measured with a coordinate measuring machine, and residual stresses are measured using x-ray diffraction.

Fabrication of Temperature-responsive Pluronic F127 Nanotubes

Haikun Xu, Advisor: Prof. Satya Shivkumar


Synthetic hydrogels based on Pluronics have been widely used as novel biomaterials in diverse medical applications because Pluronic block copolymers (PBCs) can undergo a reversible sol-gel transition in response to temperature, which means they can self-assemble into micelles at concentrations above the critical micelle concentration (CMC) and critical micelle temperature (CMT). Recently, the use of PBCs as drug delivery vehicle to treat multidrug-resistant (MDR) cancers is a rapidly developing area for cancer chemotherapy. One of the problems encountered with the use of PBCs is that the micelles disassociate at low concentrations. In order to improve the stabilization of the Pluronic micelles, chemically cross-linked hydrogels composed of Pluronic F127, water-soluble tri-block copolymer of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), were synthesized by a photo-crosslinking method. In brief, Pluronic F127 and triethylamine were first dissolved in dichloromethane, then added acryloyl chloride in a drop-wise manner. The reaction was under stirring and nitrogen purging through the system at room temperature for 48 hours to form di-acrylated Pluronic F127 (DA PF127). The DA PF127 macromer was dissolved in deionized water to prepare a sol. In the template-assisted method, anodized aluminum oxide (AAO) nano templates were initially soaked in the sol, and crosslinked subsequently upon exposure to UV light. A diverse range of hydrogels with different cross-linking densities and mechanical strengths could be produced by controlling UV irradiation time. After crosslinking, the morphology of the Pluronic 127 nanotubes and nanofibers were examined by scanning and transmission electron microscopy. Swelling ratio and rheological behaviors of Pluronic hydrogels were investigated.

Study on inter rules of absorption and diffusion on Carbonitriding Process

Yuan Xu, Liang He, Advisor: Prof. Richard D. Sisson Jr.


Carbonitriding is a widely used industry surface hardening processing while only a few study of the processing rules have been shared. This paper is aimed to study on the internal rules of the absorption and diffusion stages of carbonitriding process. AISI 8620 and AISI 1018 were chosen to help developing the understanding of mass transfer and diffusion mechanism in this process. A simulation of nitrogen diffusion in the steel has been developed as Carbonitride Tool, it was used to predict the carbon and nitrogen concentration profile, and the predictions were also compared with the industrial experimental results. Also, we aimed to build a data base for the standard carbonitriding process, in order to provide useful data for heat theaters to make a good reference for their design propose.

Microstructural Development during the Nitriding of Low Alloy Steels

Mei Yang, Advisor: Prof. Richard D. Sisson Jr.


The state of the art for controlling the nitriding process is to measure and control the nitriding potential in the atmosphere to define the composition and phase distribution at steel surface. The experimental Lehrer diagram for pure iron is widely used in industry to specify the nitriding potential for nitriding process. However, applying the pure iron Lehrer diagram for alloy steels can lead to incorrect results because of phase stabilities in alloy steels. Customized Lehrer diagram for AISI 4140 has been developed by using CALPHAD approach to predict the relationship between the nitriding potential and the phase development at different temperatures. In addition, the microstructural development during the nitriding of quenched and tempered low alloy steel has been experimentally investigated to verify the AISI 4140 Lehrer diagram. The results are in excellent agreement with the Lehrer diagram predictions.

Highly Controllable Fabrication of CNT Arrays for Interfacial Mechanical Properties Investigation

Yuqin Yao, Advisor: Prof. Jianyu Liang


Interfacial properties of nanostructured materials have been vigorously studied by scientists and researchers because of their important role in understanding the unique behaviors and devising novel applications of those materials. In this report, arrays of carbon nanotubes( CNTs) embedded in anodized aluminum oxide (AAO) templates have been utilized as a platform to study mechanical interfacial properties of importance to nanoimprinting and nanostructured reinforced composites. In order to systematically and experimentally study the interfacial mechanical properties, a highly controllable fabrication protocol to create uniform and free standing CNT arrays with well-defined morphology has been developed based on the previously well-studied template-assisted chemical vapor deposition method (CVD). The microstructure and the morphology of the CNT based nanocomposite materials are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The influence of fabrication conditions on the microstructure and the morphology of the nanomaterials, such as the property of the AAO templates, the CVD growth conditions, and the post growth treatments will be reviewed in detail. The effect of the material morphology and microstructure on the measured interfacial mechanical properties will be reported.

Metal Recovery via Automated Sortation

Hao Yu, Advisor: Prof. D. Apelian


There is only a finite amount of resources on this planet, and inorganic materials are not renewable. This is further exacerbated as our demand for resources is dramatically increasing. Through recycling we have the opportunity to reduce the consumption of our limited resources, reduce energy usage, reduce air pollution and water pollution.

Current identification methods for metal recovery and recycling rely on a chosen property of the material in order to sort it.  Typical sorting techniques include density separation, magnetic separation, hydrometallurgical processes, etc. However, nothing about the chemical composition of the materials being extracted in these processes is actually known. Today, sensing techniques have enabled determination of the chemical make up of alloys in real time.  This creates opportunities within the field of recycling to upgrade the value of waste stream by intelligently separating out unwanted materials leaving behind the desired metal.

The principal goal of this research is to create an automated sorting system to recycle high-value metal scrap. Typically, a sorting system consists of three steps: feeding, identification and separation. NIST-ATP has initiated a project to explore a sorting technology, which involves the use of X-ray fluorescence and transmission to detect chip composition and defects. WPI will focus its sortation project on the feeding and ejection steps. Moreover, the optimized feeding and ejection methods we will establish can be used with any identification methodology, and not only XRF.

Review of nondestructive evaluation of case depth on steels

Lei Zhang, Advisor: Prof. Richard D. Sisson Jr.


Case depth is an important feature in the research of case hardening that is a heat treatment process, improving wear resistance without sacrificing toughness. The nondestructive methods are necessary in measuring the case depth for the requirement of fast and online test in industry, which are analysis techniques used in science and industry to evaluate the properties of a material, component or system without causing damage. The different nondestructive evaluation methods on the case depth of steels, such as the magnetic Barkhausen emission (MBE), ultrasonic, remote visual inspection and eddy current are introduced in the review. Among these technologies, MBE and hysteresis loop analysis have proved their potential as nondestructive evaluation technique for microstructural characterization and assessment of residual stresses in ferromagnetic steels. The hysteresis loop shows a distortion with a sudden reduction in the rate of magnetization before approaching the maximum magnetic flux density indicating surface hardening, while the systematic changes in MBE profile indicate the microstructural variations with in the case. In the future, a reliable technology based on the MBE will be studied.

April 1, 2011

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